Tank Overflowed - Advice Needed

[denverjon]

So last night I had something happen that I've never seen in my 10 years of reefing. I came downstairs to find that one of my returns had backed up and, as a result my tank overflowed. I can't figure out how this could happen.

I have two return pipes running from my tank into my sump. One thing I have noticed over the last several weeks is that their would be a loud "burp" of air being released from one of my pipes every minute or so. It sounded to me that air was being trapped and then released through the pipes.

After the flood last night, i removed one of the stand pipes from the overflow to see if there was an obstruction. There wasn't but when I removed it, there was a giant "burp" and water started flowing freely through it again.

I've got to believe that somehow air caught in the pipe and caused it to backup. Does that make sense?

Thanks for your thoughts!

 

[mojo]

sorry to here. I am not sure why this would of happened. how far is your drain to the sump ?

 

[denverjon]

It probably four to five feet total. The puzzling thing is that it's all downhill, so you would think gravity alone would keep the water flowing.

 

[mojo]

is there a hole on top of your durso ? did it clog with salt creep ?

 

[denverjon]

There is a hole on the top of my durso, but I'll have to check to see if it clogged. Could that make a difference?

 

[mojo]

yea, it needs to be open or it cant pull in air. Creating a vaccuum affect as the water flows down.

 

[denverjon]

I just checked the hole in the durso and it was about 90% obstructed. There looked to be a small shell or something similar in there.

 

[denverjon]

I meant to say 90 percent.

So why would that cause the drain pipe to overflow? Event without a vacuum, wouldn't gravity force the water to flow downstream into the sump?

 

[bct15]

The volume of water that can lass through a hole is dictated by the area the hole occupies. This relationship is not a linear one, double the area allow four times the flow. A reduction of 90 percent will reduce the allowable flow almost down to nothing, each time you half divide the flow by four...50 percent = 1/4, 25 percent = 1/4, 12.5 percent = 1/4. which gives you flow rate 1/56 less than you had going through ther before, if your return pump flow rate is higher than this number than an overflow or empty sump is inevitable.

 

[Troylee]

How far is your drain pipe below the water in the sump??? If it's more than 1" yeah it would be a problem with the air line plugged... When you run a drain like a full siphon with zero air introduced to the durso it's very hard to get it to start if the drain is submerged more than a inch.... Cut that pipe down so only like 1/2" is under water in the sump and it should help prevent this from ever happening again....

 

[Troylee]

And I mean when the sump is in action "return pump on" if your sump is let's say 20" tall ad the water line is 10" when in service your drain from the top of the sump down should not exceed 10.5" if that makes sense... I can snap a picture of mine if you need....

 

[bct15]

The volume of water that can lass through a hole is dictated by the area the hole occupies. This relationship is not a linear one, double the area allow four times the flow. A reduction of 90 percent will reduce the allowable flow almost down to nothing, each time you half divide the flow by four...50 percent = 1/4, 25 percent = 1/4, 12.5 percent = 1/4. which gives you flow rate 1/56 less than you had going through ther before, if your return pump flow rate is higher than this number than an overflow or empty sump is inevitable.

Oops thought the shell was blocking flow of water not air, same concept applies for air as well...and actually the air is what pushes the water down your drain (a little complicated to explain) but if the amount of air flow is reduce then the amount of water that can be pushed will be reduced by a linearly proportional amount so you will still experience a similar amount of flow loss but a little less.

Similar concept to placing you straw in a liquid then placing you finger over the other end, when you loft your straw out of the water the liquid will stay in the straw because there is no pressure difference and air cannot enter the straw to push the water out...

 

[denverjon]

Thanks for all of the advice. It's starting to make sense.

Troylee - Yeah, my pipe is probably 5" below the sump water line, so I'm going to cut it back.

 

[Troylee]

Yeah that's way to far man..: it will hiccup like you were saying... You will see once you cut it that it starts very easy and will be super quiet to what you had before..

 

[denverjon]

Sounds good. Thanks

I just started it back up and it seems to be working ok now.

Now the cleanup begins!